Preheat oven to 375ºF. Line cookie sheets with parchment paper or silicone baking mats. Whisk flour and salt together in a small bowl. In a large mixing bowl, on medium-high speed, beat butter until creamy, about 2 minutes. Add both sugars gradually, beating until light and fluffy, about 3 minutes. Add extract and egg and beat for another minute. Mixture should be very light and smooth. Add about one-third of flour mixture and mix on low speed. Gradually add remaining flour, mixing just until blended. Place dough in cookie press. Following manufacturer’s instruction for your cookie press, form desired shapes 2 inches apart directly onto lined cookie sheets. Sprinkle peppermint powder over formed cookies. Bake until just light and golden brown around edges, about 10 minutes. Immediately slide parchment onto wire racks to cool.